The sinister John McDonnell is trying to sink the Remain campaign – good luck to him

How many politicians genuinely reinvent themselves? Is it even possible in the era of Google searches, internet caches and Twitter?

In fact, almost every top flight politician does it to an extent. It's not necessarily, and not always, opportunism or cynicism; we all change our minds on a number of issues over the course of our lifetimes. It's an inevitable part of growing up and growing old.

Sometimes we esteem too much the unswerving principle of the individual, not fully realising that we are building disillusion and disappointment into the system. Nye Bevan, the iconic hero of the Labour Left throughout the 1940s and 1950s, reduced many of his followers to a tearful rage when he reneged on his previous commitment to unilateralism and decided to endorse Britain's independent deterrent.

Neil Kinnock, who consciously modelled himself on his hero, Bevan, followed the same path, extolling with fiery passion, at different points in his career, the cases for and against nuclear weapons. There were many factors behind the ultimate failure of both men to reach the highest office, but arguably their willingness to be open-minded and flexible to a degree that infuriated their followers played a part in their eventual failures.

Watch | Cameron and Corbyn urge voters to stay 'in'

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Less dramatic reinventions by David Cameron (ardent eurosceptic when he was first elected, to today's "Well, if you love the EU so much why don't you just marry it?" champion of a Remain vote) and Peter Mandelson's transformation from cynical political manipulator to... Well, anyway, politicians change over time.

It seems the more gradual, the less dramatic the change, the less likely we are to notice the transformation over the years.

So, John McDonnell, eh?

Like the Seventh Cavalry (without the designs on racial slaughter of a native population, naturally) riding over the hill to the sound of trumpets, standard fluttering proudly in the breeze, the Shadow Chancellor has ridden to the nation's rescue. Who says so? Well, John McDonnell, since you ask.

He's here to rescue the EU referendum debate from Tory infighting (because John is lucky enough to hail from a party where such a thing is unheard of) and to make the positive case for the UK's remaining in the EU.

And here is the heart of the matter, the Holy Grail, if you will, if you want your public to buy your makeover: they've got to believe it's genuine.

And to many people in the Labour Party, and perhaps among the TV viewing public, this transformation into a calm, moderate, sensible voice of reason is entirely believable. If you're an idiot, I mean.

I've rehearsed McDonnell's charge sheet before but it's worth refreshing our memory, just to remind his apologists of exactly how unfit for office he really is. And by "office" I mean a seat in the Commons, let alone his current job on the front bench, let alone (May God Almighty, in His infinite wisdom have mercy upon all our souls) Chancellor of the Exchequer.

Watch | John McDonnell speaks at rally as 'Heathrow 13' protesters in court

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This man who aspires to lead a once great party of government believes that workers in dispute with their bosses should spit in those same bosses' tea. Funny, right? And yet pathetic and infantile beyond what should be considered normal political behaviour. Or even normal adult behaviour.

And now this self-styled father of the nation, this avuncular Everyman hopes to win the EU referendum for his party.

Or does he?

Given the absolute certainty that McDonnell's makeover is one hundred per cent fraudulent, how can we be sure he even wants the Remain side to win? He's never been a fan of the EU before now, and his boss, the man McDonnell sees as keeping his seat warm for the Shadow Chancellor, is known to be, at best, a lukewarm enthusiast, having been forced into that position by his Shadow Cabinet.

How such a divisive, sectarian class warrior like McDonnell can claim to want the same thing on June 23 as David Cameron is enough to make one strongly suspect he's a plant, a sleeper agent recruited by Vote Leave some years ago.

For those who actually do want a new kind of "honest, straight talking politics", John McDonnell must surely be their worst nightmare. A more naked, cynical attempt at reinvention has never been made.